line. One variation of identifying the calling party on direct-dialed long-distance calls is a party code, usually a single digit inside a circle displayed on the phone's number tag. The dialing sequence for such calls is "1" (access number for DDD), the party code, the area code, and the desired number (1 + party code + area code + number). Systems which identify the caller's name and address to emergency telephone numbers (such as Enhanced 9-1-1 in North America) may be unable to identify which of multiple parties on a shared line placed a distress call; this is aggravated by the use of old mechanical switching equipment for party lines as this obsolete apparatus consistently provides no caller ID and often also lacks automatic number identification capability. When the party line was already in use, if any of the other subscribers to that line picked up the phone, they could hear and participate in the conversation. Eavesdropping opportunities abounded. If one of the parties used the phone heavily, then the inconvenience for the others was more than occasional, as depicted in the 1959 comedy film Pillow Talk. Dialing one's own number and hanging up would make all phones on the network ring, resulting in the residents on the system (sometimes a half a dozen or more) all answering the phone at the same time. This was sometimes used as a form of prank call, but could also be employed as a form of early warning system for the immediate area, a user could alert all local residents at once. Party lines were typically operated using mechanical switching systems which recognized certain codes for revertive calls; these no longer work on modern electronic or digital switchgear. Party lines are not suitable for Internet access. If one customer is using dial-up, it will jam the line for all other customers of the same party line. Bridge taps made party lines unsuitable for DSL, even in the few areas where distance from the central office did not already preclude its use. Telephone companies typically do not allow client-owned equipment to be directly connected to party lines, posing an additional obstacle to their use for data. Barbed wire telephone lines Barbed wire telephone lines were local networks created in rural America around the turn of the 20th century. In some isolated farming communities, it was not cost-effective for corporations to invest in the telephone